1. Field of Industrial Utilization
The present invention relates to a control device for an electrically driven telescopic antenna in which the length of the telescopic antenna element is controlled by counting an altered waveform of a rectified current that is generated during the rotation of a DC motor which is a driving source of an antenna element extending and retracting mechanism.
2. Prior Art
In one example of a conventional control device for electrically driven telescopic antennas, the rotation of an antenna driving motor is detected by a rotation-detecting mechanism which is, for example, a lead switch system. A pulse signal series that corresponds to the rpm of the driving motor is thus obtained, then the obtained pulse signal series is counted by a counting circuit after waveform shaping. The driving motor is controlled on the basis of this counted value so that the extension/retraction action of the antenna element is controlled.
In the conventional device described above, the rotation of the driving motor is detected by a rotation-detecting mechanism which is a lead switch system, etc. Accordingly, detection errors tend to occur, and the mechanically operated components are easily damaged. As a result, the antenna extension and retraction operations become unstable in a relatively short period of time and a highly reliable operation is not expected.